1. Field of the Invention
The present invention relates to a centrifugal pellet dryer having an exhaust fan associated therewith for removing moist air and more particularly to such an arrangement in which the exhaust fan is mounted directly on top of the dryer housing and in direct communication therewith with the fan impeller being connected directly to the dryer rotor shaft. The dryer also includes a unique rotor structure that is quite rigid due to its welded construction and its main structure being square tubing.
2. Description of the Prior Art
Conventional centrifugal pellet dryers use a bladed rotor to sling wet pellets against a peripheral screen which retains the pellets while surface moisture passes through the screen. The blade structure of the rotor is slanted for moving the pellets upwardly as they are slung against the screen with the pellets being discharged through a discharge chute which communicates with the upper end of the screen. The rotor also acts as a fan and blows moist air out of the pellet discharge chute with the moist air hindering the drying process particularly when the relative humidity in the dryer is high. This type of dryer is disclosed in U.S. Pat. No. 3,458,045, issued July 29, 1969 to Vernon E. Dudley. As an improvement to the above described dryer, a blower has been communicated with the periphery of the dryer adjacent the upper end thereof to exhaust moist air. This arrangement reduces moisture carry-over characteristics but it is expensive, requires much more floor space, supporting structure, duct work and maintenance.
Other dryers relating to the present invention are shown in the following U.S. patents:
U.S. Pat. No. 2,274,948, N. Ahlmann PA1 U.S. Pat. No. 2,688,807, J. H. Ginther PA1 U.S. Pat. No. 2,869,249, H. Kemp PA1 U.S. Pat. No. 3,199,215, D. R. Jesse et al PA1 U.S. Pat. No. 3,724,091, J. A. N. Rousselet PA1 U.S. Pat. No. 4,126,947, J. Labouygues
These patents disclose dryers utilizing blowers to circulate air therethrough. The Jesse et al patent discloses an arrangement in which the blower is located laterally at the bottom of the shell and the Kemp patent discloses an air circulating device for a dryer. The Ginther patent discloses an exhaust fan associated with a dryer.